Add smoke tests for model configs

[pwang347]

Flake busting #323242

[Copilot]

Pull request overview

This pull request adds a new end-to-end smoke test suite that validates chat model configuration selections (reasoning effort + context size) are forwarded to the LLM request payload, using the existing mock LLM server infrastructure and new automation helpers for interacting with the chat model picker UI.

Changes:

• Register and run a new “Chat Model Configuration” smoke suite in the Electron (non-remote) smoke test run.
• Add chat automation helpers to select a model and its configuration options via the model picker UI.
• Extend the mock LLM server to expose captured request bodies for assertions, and add a dedicated mock model that supports both reasoning effort and a long-context tier.

Show a summary per file

File	Description
test/smoke/src/main.ts	Wires the new chat model configuration smoke suite into the Electron smoke run.
test/smoke/src/areas/chat/chatModelConfig.test.ts	New smoke suite that drives the model picker UI and asserts forwarded reasoning.effort and context-management threshold in /responses.
test/automation/src/chat.ts	Adds automation methods for selecting a chat model and interacting with the model configuration dropdown.
scripts/chat-simulation/common/mock-llm-server.ts	Adds a mock model with config pickers and exposes captured request bodies via getRequests().

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Low